“Cumulative Effect” of Cold Vortex Precipitation in Northeast China in Early Summer

Using precipitation observations in Northeast China (NEC) in May and June from 1960 to 2012, an objective identification method for cold vortex activity in NEC is applied to analyze the cold vortex activity in NEC and its impact on cold vortex precipitation in early summer. Results show that periodicity of the cold vortex activity from May to June is 3-7 days with the character of frequent occurrence, and the precipitation induced by the cold vortex accounts for 62.5% of the total rainfall in NEC. A cold vortex monthly rainfall intensity index is defined, which is consistent with the interannual variability of monthly rainfall in the same period. Early summer precipitation pattern in NEC is similar to the leading mode of EOF decomposition of cold vortex precipitation. The first two leading modes of EOF decomposition present a pattern similar over the entire NEC and a pattern that is contrary in the northeast and southwest of the NEC, respectively. The two leading modes account for 46.8% and 42.7% of the total variance, respectively. The concept of "Cumulative Effect" of cold vortex precipitation (CECEP) is proposed. The CECEP can reflect the characteristics of spatial distribution of summer precipitation anomaly in NEC in general, and further reveal the climatological characteristics of the cold vortex activity.